So what are you asking?  Who is "they"?  The new owner?  So the new owner has tax liens against them with an address of a property that they supposedly didn't own prior to 2018?

They might have been renters.  Or buying on a land contract.  Or living with their parents?  Even tho there is SUPPOSEDLY a 10 year limit on liens w/o state or federal re-issuing something, I always at LEAST list the liens with a caveat "copies available upon request.  These are all more than 10 years old" or something like that.  If there are only a couple, I just take the copies and include them.  It's worth a couple of bucks for peace of mind.